Yes it can be installed on Windows Vista. There is no limitation.
I run JBoss AS on both a 32-bit Vista (laptop) and 64-bit Vista (desktop).
Be aware that the EULA you agreed to when you installed Vista (or configured if it came on your box) limits you to 10 incoming connections, therefore you should not deploy your web app to Vista in production if you have more than 10 users. This same limitation applies to XP.
One more gotcha - use the latest version of JDK 5 or JDK 6, earlier versions had issues when running on Vista.